Image heating apparatus and controller

Abstract

An image heating apparatus has a heat generating element for generating heat upon electric energization; a substrate supporting the heat generating element; a temperature detecting member for detecting a temperature of the substrate; an A/D converter for A/D conversion of an output of the temperature detecting member; a photo-coupler for converting an output of the A/D converter to a light signal and outputting the light signal; and an abnormality detecting unit for detecting an abnormal temperature on the basis of an output of the photo-coupler.

What is claimed is:  
     
       1. An image heating apparatus, comprising: 
       a heat generating member for generating heat upon electric energy supply thereto;  
       a base plate for supporting said heat generating member;  
       a temperature detecting element for detecting a temperature of said base plate;  
       A/D conversion means for converting an output of the temperature detecting element to a digital signal;  
       photo-coupling means for converting an output of said A/D conversion means to an optical signal; and  
       abnormality discriminating means for discriminating abnormality of said apparatus on the basis of an output of said temperature detecting element through said photo-coupling means, wherein when said abnormality discriminating means discriminates an abnormality the electric energy supply to said heat generating member is stopped.  
     
     
       2. An apparatus according to  claim 1 , further comprising control means for controlling the electric energy supply to said heat generating member so that output of said temperature detecting element is at a predetermined level. 
     
     
       3. An apparatus according to  claim 2 , wherein said control means is responsive to an output of said temperature detecting element through said photo-coupling means to control an amount of the electric energy supplied to said heat generating member. 
     
     
       4. An apparatus according to  claim 1 , wherein said base plate mainly comprises ceramic material. 
     
     
       5. An apparatus according to  claim 1 , wherein said temperature detecting element detects the temperature at a side of the base plate which is opposite from the side supporting the heat generating member. 
     
     
       6. An apparatus according to  claim 1 , further comprising stopping means for stopping electric energy supply of said heat generating member when said abnormality discriminating means detects an abnormal temperature. 
     
     
       7. An apparatus according to  claim 1 , wherein said image heating apparatus is used as a heat-fixing device in an image forming apparatus. 
     
     
       8. An apparatus according to  claim 1 , further comprising shut-off means for stopping supply of the electric energy to said heat generating member upon the abnormality of the apparatus.